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Would This be a Suitable Phase Converter for a M-G 10EE?


Jul 2, 2002
Gaithersburg, MD USA
I have the oppurtunitty to purchase a new Phase-A-Matic 3-5 HP Heavy Duty Static Phase converter (HD model #...PAM-600HD) at a very attractive price. I was researching the product and along w/ using it as a static, they advocate advocate using an idler motor in conjunction for a rotary phase converter setup. I have a 5 HP idler motor available to me.

Is this a useable setup? Or should I hang on and build a 7.5 HP rotary converter?

This is for a home shop. The lathe is a 1945 10EE w/ a M-G setup. The DC drive motor is 3 HP. The AC motor nameplate requires 13.2 Amps at 220V (no HP given), so I figure its not quite, or around a 5 HP motor driving the M-G set.

Here is some info for Phase-a-matic...

Static Conv brochure (see method 2...using idler for a rotary converter)

Instruction sheet (has notes for adding idler motor to make it a rotary)

Technical Notes

Any feedback on feasibilty is greatly appreciatted.

I have read where Donie ran his MG on a 7.5 HP static converter. In static mode, 5 HP isn't going to be enough. However, if I use an idler motor I think this would be doable...if the 10EE's AC motor is WYE wound.

Thanks, Mark
"I have read where Donie ran his MG on a 7.5 HP static converter. In static mode, 5 HP isn't going to be enough. However, if I use an idler motor I think this would be doable...if the 10EE's AC motor is WYE wound."

Don used a Cedarberg 7.5 HP heavy duty static on his M-G machine.

You will likely need a 7.5 HP rotary for your M-G, started using an appropriate circuit, or a lower powered static.

It doesn't matter what winding configuration the 10EE's motor employs ... Delta or Wye ... as there is no neutral in a 10EE, only L1, L2 and L3 (L1, L2, L3 and L4, for two-phase models).
The only problem I had was starting at over 1200rpms with a heavy chuck. The AC motor would pull down enough to lose DC voltage and the switches in the DC circut would pop out.
I have a another Motor Generator unit with a cooked DC end. I start that with the 7.5 hp Cederburg static converter and run the Monarch, Hardinge and Moore off that. It has been working really well.
The EE will start at any speed setting now and seems to run a little smoother.
I think an idler motor would be helpfull for you.

Well if you suggest a 7.5 HP RPC. Are you saying then w/ this 5 HP RPC that I will only get 80% of power? I think I could live w/ that.

I have been watching for a 7.5 HP idler to show up for a reasonable price and it hasn't happened yet. Although I havn't turned up every stone I have been watching and asking around for awhile now. I'll keep looking. but until I get a 7.5 RPC together, I was thinking that this would be a reasonably inexpensive route to go for the short term.

If anyone else is using a 5 HP RPC to power their 10EE, esp a M-G unit, please relate how its working out.

Thanks very much, Mark
Dont know for sure, it seems like you get less than 80% power with the static converter alone,
I ran the MG EE for a long time with just the static converter.
I think you will be happier using an idle motor, the machine just performs better. If the 5hp converter will start your machine, you can sure run it that way untill you find an idler motor.
There is a pile of practicaly free 3phase motors around here at the scrap yards. If you go to the electric supply places, they want $200 and up for them.

An M-G 10EE is rated 4.5 kW (electrical) in for 3 HP (mechanical) out.

At 100 percent efficiency, that 4.5 kW is a little more than 6 HP.

At a more realistic 80 percent efficiency, that 4.5 kW is a little more than 7.5 HP.

WiaD and Modular machines are more efficient. But, they're also single-phase.

Except for the coolant pump motor, of course.

If you use your M-G machine consistently below its maximum rated output, 3 HP, you could well be satisfied with a 5 HP rotary. This could give 2 HP of the machine's rated 3 HP.

However, if you use you M-G machine consistently at its rated output, then do consider a 7.5 HP rotary.

A benefit of WiaD and Modular machines is the exceptionally low idling power ... just a few amps. It's when full rated power is demanded does the line current dramatically increase.
I have a 5 hp phase a matic and have run my MG with it, but only for short periods of time and not for anything heavy.
Phase O matic has a standard and heavy duty models.

The standard is just a start capicitor and relay to get the system going (at least that what the one I took apart looked like). I assume the Heavy duty static line has a run capicitor to help ballance the wild leg out a little better.

Either way, set it up with a slave motor and find a few oil type capicitors to balance the wild leg based on the slave motor you chose.

I run my 3 hp MG machine on a 5 hp home built rotary and it lets you know when you start the machine up, but never trips the breaker.

Also, dont put the wild leg on the circut that pulls in the primary control relays. The wild leg is alway weak and may not shut the relay efficentyly. You will know from the buzzing or all together lack of function. A few wire swaps and a little trial and error go a long way on this one.

I syour 5 HP phase-a-matic used strictly as a staic converter? Ot do you have it hooked up w/ an idler motor?

How is the performance under load? What about stops and starts in succesion?

I should have said that it was a Phase-a-matic 5 hp heavy duty rotary converter with no idler.
I do not notice any complaints when I turn it all on. But like I said I really haven't used it much yet, I still have to overhaul it and make some space for it. It seems to me that an idler would be a good idea for your 5 hp static.
I Just run my MG EE off the old MG unit as an idler with no fancy stuff,
It runs really good, without any problem. Might be better trying to balance the wild leg, but I dont want to take time to mess with it. It just works.